1,25-Dihydroxyvitamin D3 increases epidermal growth factor receptor gene expression in BT-20 breast carcinoma cells.

In the breast cancer cell line BT-20 which displays a high number of Epidermal Growth Factor Receptors (EGF-R), we have previously observed that 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) at low concentration (0.1 nM) significantly reduces the proliferation rate while it upregulates the EGF binding capacity. The aim of the present investigation was to analyze EGF-R mRNA expression in 1,25-(OH)2D3 treated BT-20 cells. It is found that in cells treated for several days, the EGF-R mRNA levels are increased in relation to the dose from 0.01 to 1 nM. To investigate the time course of the response, cells received the drug only once and were harvested at different times. The data suggest that the stimulation of EGF-R mRNA expression is dose- and time-dependent. Therefore, the increased EGF binding capacity previously demonstrated can be related to the increase of EGF-R transcript levels.